Wierdest problem you'll ever see

[Quad]

check this out:

i have a friend who has a lamp near his monitor. whenever he turns on the lamp, his keyboard becomes unresponsive. this is really wierd because the lamp and keyboard are totally unrelated. in order to get his keyboard working again, he just takes out the ps/2 connector and plugs it back in.

the lamp and the psu are both connected to the same powerbar. he also has a high quality 350w powersupply.

how could this be possible? if the powersupply was suspect, wouldn't other parts of the system also be affected?

on another note, he also has 2 mice connected, 1 usb and 1 ps/2. both are able to control the cursor. he said that he plugged in the ps/2 after the usb and both worked.

any idea what's going on?

 

[odog]

the mouse thing isn't weird? i've had three mice hooked up to my system at once, 1 PS/2 and 2 USB. al were able to control the cursor.


the lamp is obviously messing with the power, and this is effecting the voltage going to the PS/2 connector.

 

[jamarno]

Turning the lamp on may be causing a current surge that sends a signal into the keyboard. Moving the keyboard and its cable farther away may help. Wrapping the cable around a choke (Radio Shack's "split" toriod) near the computer end may also help, but I doubt it.

I'd try plugging the lamp into a separate outlet or surge protector because by having both devices connected to the same power bar, there's not much surge protection to those devices. The only surge protector that will stop this type of problem is the kind containing an EMI filter, which stops fast-changing signals and not just excess voltage the way low-quality surge protectors do. The computer's power supply should also contain such a filter, not only for protection but also to keep the computer from sending out signals through the AC cord. Many supplies just have the EMI components left out.

 

[GD695372]

Thanks for the info. Would you happen to know if I could get some sort of adapter to plug my receiver into soo that it wouldn't pick up a 60hz buzz from the electrical line?

 

[jamarno]

60 Hz is the only frequency that can't be removed with a line filter because 120VAC works at 60 Hz. Try reversing any 2-prong AC plugs, one at a time, until hum decreases. Another major cause of hum is ground loops, where imperfect grounds cause feedback, and for them you can try connecting a ground wire between the chassis of each piece of hi-fi equipment. However you don't want to do this with anything that uses a "hot" chassis, as almost all TVs do, because that will cause an electrocution hazard. Another method is to disconnect the ground connection at one end of some of your shielded audio cables, and if you don't feel like cutting your cables, there are adapters for this. There are also audio coupling transformers made especially for eliminating ground loops in cars, and one of those sold by Radio Shack is of very good quality.

 

[GD695372]

Well I kinda figured that I wouldn't be able to get rid of the 60hz frequency, but thanks anyway.